Motor vehicle bodywork, in particular in the body proper, includes tubular parts such as pillars beside openings, side members, . . . , which constitute significant paths for propagating and delivering noise of various kinds into the vehicle cabin, thereby degrading passenger comfort.
Providing sound insulation for such tubular parts thus poses a problem, given that these parts are also of various shapes with varying sections, and may themselves be built up by assembling together a plurality of parts.
In order to limit the propagation of such noise, vehicle manufacturers have for a long time been closing off the inside sections of tubular parts by locally injecting a composition that can be caused to expand chemically so as to create a foam which comes into contact with the inside wall of such a part and form at least one sound partition. Foam is injected through a hole pierced in the part after the vehicle body has been painted. That solution generally gives satisfaction when the part, or the portion within the part, where the partition is to be installed is generally in the form of a tube having a right section that is substantially circular and of diameter that is not too great. However, that solution presents the drawback of a hole being pierced after the part has been painted, which constitutes an additional operation and which can run the risk of corrosion if the part is made of metal, and it requires the use of special equipment for injecting the foam.
U.S. Pat. No. 5,642,914 discloses a sound insulation device comprising a thermally expandable material that is generally in the form of a flat ring fitted to the periphery of a partitioning insert. The ring is obtained by extrusion or by molding, thereby giving it in advance the shape of the outline of the partitioning insert.
Document WO 01/83206 discloses a sound insulation device in which the thermally expandable material is molded on the periphery of a partitioning insert or is in the form of a strip which is bonded to the periphery of said insert by adhesive or by means of staples.